A glass-bottomed jet ... sounds as cartoon-like as a flying car but a new iPad app created by Delta Air Lines has a nifty feature called just that, which allows passengers to watch the ground below as they fly.

It's not live footage but the "glass bottom jet" section of its new Fly Delta for iPad app combines maps, satellite imagery, photos, social media updates and the aircraft's position to highlight landmarks below.

The app, available to passengers on its 800 Wi-Fi enabled aircraft, also features all the usual stuff including destination guides, check-in, itinerary planners, seat plans and so on – but the "glass bottom jet" is the fun bit that's getting the online gizmo community talking.